The present invention relates to a method for manufacturing an in-mold coating product that easily improves the hermetic seal for a mold having an in-mold coating cavity.
A resin molding product, such as a door pillar garnish for an automobile, is typically manufactured by performing in-mold coating in which a substrate is first molded and a coating is then applied to the substrate. When charging a mold cavity with a coating material, which has a low viscosity, to apply the coating material to the substrate during in-mold coating, there is a tendency for the coating material to leak out of the mold cavity. Therefore, an auxiliary cavity extends around the entire mold cavity. Resin is charged into the auxiliary cavity so that the molded substrate is provided with a structure for preventing the leakage of the coating material. However, as the resin in the auxiliary cavity cools during the period from when the substrate is molded to when the coating material is charged, a gap is formed between the mold and the resin in the auxiliary cavity. As a result, the coating material may leak out of the gap.
Referring to FIG. 8A, to solve this problem, resin is charged into a substrate cavity, which is defined between a movable mold piece 101 and a fixed mold piece 102, to mold a substrate 103 in the prior art. The molded substrate 103 includes a projection 103a. Then, referring to FIG. 8B, the movable mold piece 101 is moved in a mold opening direction to form a coating cavity 104 into which a coating material is charged. The projection 103a closes the gap between the substrate 103 and the movable mold piece 101 to prevent leakage of the coating material.
Japanese Laid-Open Patent Publication No. 2003-191286 describes a groove formed in an auxiliary cavity of a movable mold piece. Subsequent to the molding of the substrate, the movable mold piece is moved in a mold opening direction to form a coating cavity into which a coating material is charged between the surface of the substrate and the cavity surface of the movable mold piece. When moving the movable mold piece in the mold opening direction, the projection of the substrate moves out of the groove and closes the gap between the substrate and the mold piece. This prevents the charged coating material from leaking out of the coating cavity.
However, in the mold of FIGS. 8A and 8B and the mold of Japanese Laid-Open Patent Publication No. 2003-191286, the same mold pieces are used to mold the substrate and to apply the coating. This results in the necessity of the auxiliary cavity, which imposes many restrictions on the shape of the resin molded product, especially, at the peripheral portion of the product.